Flaw detector means



Jan. 30, 1945 L. J. DE LANTY Erm. 2,368,119

l FLAw DETECTOR MEANS Filed Nov. 5, 1940 :5 sheets-sheet 1 Mimi;

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@e f; 6.a f @a 64 l/ Y 65 Patented Jan. 30, 1945 UNITED STATES PATENT OFFICE 2,368,119 I FLAW DETECTOR MEANS Loren J. De Lanty, Spring Valley, N. Y., and William A. Williams, Grayvllle, Ill., assigner: to Sperry Products, Inc., Hoboken, N. J., a corporation of New York Application November 5, 1940, Serial No. 364,362

' (c1. irs-iss) Claims.

This invention relates to flaw detector means for electric conductors and is especially adapted for testing airplane struts or tie rods and similar objects. One of the principal objects of the invention is to provide such a testing device which can be readily adapted to the testing of struts of varying lengths, thicknesses and end diameters.

Another important object of this invention relates to means for making rapid electric connections between the source of current to be passed through-the struts and the ends of the struts, regardless of the varying dimensions of the struts and their end members.

Still another object of this invention is to pro- 'vide means whereby the struts may -b'e quickly mounted in testing position.

Still another object of this invention is to provide novel detector means adapted to respond to differences in electric potential between points along the length of the struts with a view to obtaining the maximum output from the responsive means for any given defect.

Still further objects and advantages of this invention will become apparent in the following detailed description thereof.

In the accompanying drawings,

Fig. 1 is a front elevation showing a general assembly of our machine embodying our invention.

Fig. 2 is a front elevation of an enlarged detail of one end of the strut holding mechanism.

Fig. 3 is an endelevation of the Fig. 2 portion of the machine.

Fig. 4 is a bottom view of the potential drop measuring device for detecting transverse defects.

Figs. 5 and 6 are two views illustrating the theory of this invention.

Figs. 'land 8 are a plan view and a cross section of a typical strut designed to be tested by this machine.

Referring rst to Figs. 7 and 8, there is shown a type of metallic conductor for the testing of which our machine is especially adapted. It will be understood that this invention is not limited to the testing of airplane struts alone, but applies equallywell to a. large number of. similar articles.

However, the invention is to be described hereinafter with reference to the airplane strut I0 which has the general sha-pe in plan shown in Fig. 7 and which in section is substantially elliptic as shown inFig. 8. The strut terminates in screw threaded portions Il. The struts vary in length, width, and shape, and therefore create a. special problem in testing the same for defects such as the transverse ssure F shown in Fig. 7. While various means for testing devices of this type have been proposed, we have found that the only practical form consists in sending current through the strut from one end thereof to the other and measuring the potential drop from point to point along the length threof. l v

Our invention, therefore, consists broadly in two general parts, as follows: The rst consists in providing a supporting mechanism for the strut which will enable thetrut to be quickly placed in position for testing -in such manner that current may be passed therethrough regardless of the variations in length, width and cross-section of the particular strut being tested. Second, our invention consists in providing a special detector less leakage for any given defect than has heretofore been possible.

For accomplishing the first of lthese objects, the entire testing device is adapted to be mounted upon a tablel5 -upon which there are mounted two strut supports I6 and I1. The strut support at one end, for instance, the support I6; may be mounted on a base i6' fixed to the table, while the strut support l1 is mounted on` a base l1 movable on the table. Such movement may -be guided by a lug 34 operating in a longitudinal slot; 33 in the table. The base I1' is moved until it is approximately the right distance from base I6' to accommodate the strut to be tested, and then base I'l'is locked to the table. For this purpose, a' handle 50 may be provided on a shaft; 5| having beveled gear engagement 52 and 53 with a stem 54 into which is screwed a pin 55 extending through the table l5. A square lock-nut 56 in a similar shaped opening in the table prevents the pin 55 from rotating, and therefore rotation of shaft Sli-after handle 50 is turned serves to move pin 55` upwardly or downwardly to cause 'a flange 51 carried at the outer end of said pin to engage or disengage the table l5. To lock base n' to the table, the nangs1 is caused to engage said table flrmly. l v

When base l1' has been locked to the table at approximately the correct distance from. 'I6' to accommodate the strut to be tested, the strut is positioned on supports lli` and l1. In each support member i6, l1, there is a main bracket 25 substantially perpendicular to the plane of the table provided with a, U-shaped opening 26 (see-Fig. 3). vided a plate 2l having a similar U-shaped opening 28 within the Uf-shaped opening 26. The threaded ends Il of thex strut I0 are adapted to rest within the U-shaped openings 28 in the Back of said opening there is pro- A mais Il and I1 xespectivelnandthe pmbluniatoelecteeetrlcaleuntactwithaaidends ina'dertopasseunmtthrghtheshuta. This sbesteededbymeansofplatesllothkh deetrlc conductivity, auch as copper, fastened hdxindtheplateslandhavingaU-shlped opmirnmincdinsliththeU-abapedopeningin platelandsaidplaiebeingL-shapedand edendmdthepperumtmtplatelbymeans ufanutllnaptedtobeqlcklyscrew-threaded upontheend Mintormentwiththe mspectivepiatesl. lbrthispurposeeachmp port Ii :andH is provided a. 1118 Il (see 115g. 2) downwardly through asiat llextendingkmghxgiinallyinmetablevhenebythesupport AI`I maybemoved toward prawny rmnthesupportinordertoeifectrmeontactbetweenphteslmndthenutsll. 'Dielengimdinalmovemento! the support li or l1 relativetothebasesli'orllmaybeacemnplisbed bymelnsofnlugllhavingascrew threaded opening therein in which operates n sexsewlwhchpmiectsout oftheendofthe txbiefandmaybepmvided handleusothatcrew!! maybeturnedby turnmghandlehnnnedirecnnortheother 'Ihepotentialdmpmeamngdeviissbo'n inm.4andemnpriaeltwoaeesofpotentld eontadxanangedmparauelandtheoutputl 'thervenfextmdhigintoanamplier-A. It'ill belemthatihemntaetsoloneaetareaninsed inrelatinnwithrespecttotheoontads oftheoiherset. '.lhsanovelenn- .sirudionwhiehyeldsxesultsnotheretnforeobtained. Thereaamorthisvillbediscledby amdyofthegusandli. Refer-ringtoi'iI-ityillbeneenthatntads each set o! contacts arranged in line trans maelywithmqaecttnaelonshxdinalmxisof thetrut. Mpairofntactgasorinstln. -ooninctsl,il,ismalinepanlleltothelolx tudinalnxisottheemdtmtorundertest. Inthis armement, if .a nssure 1" is encountered there villbeanincr'easeddmpinpotentialbet'een oontacts2xnd,butthecurrent,tryngto ndeasierpaths.1illveryreadlybeableto nndshorterpathsbetweeneontactsiluand ontheonesideandntactsiLiSandilon theother-side. Inother vords,inthearrnme mentshowmtheareatleasthaliadomi abort-circuiiing paths which the current may ollowinpretermtothehighresistanpath bet'eencontactslnnd. Muchoftheeurmntdoestahetheeasierpathnndihe'reiore there lesultsalesseroutput due to greater leakamasaresultni'theplm'alityoshortdmrit PlthShlnmightother-'sehavebeenobtained hadthesepathsmtbempresent If.nml,the ntactsal'arranmedinstaggeredrelaas dnwnngihmtwillbeapparentthat thesamecoverageeanbeobtanedasinm.5 withhnlf the number-of contacts, `and therefore with a much mailer number `of short circuit- Ifweeliminateoontwts il, 62,65

andilitwllbeseentlntthesameooverage sobtainedasbefore,mttbenumberofsnrt increasedldmpinpoteniialwillbeamrentbeandand the only short nimritngpathwhichispresentinthisparcularinstanoevillbethatwhchexistsbetween oontactsfillndil. Inthismanneramuchsimtolcamesupportlinrhtoammchormove' away from the other `(mirent. imm any suitable source may be suppiedtnthenantactsntopasscunmtihrmrhf tbezstrutwhichsnowsnppurdintesngpiwsenftheshutwhichmaybeeamedbythe presen-odeectsm'edetectedbymeansna potential:dropevieenfspecul'de--` sign. Thecnnentwhidlissuppliedtothestrut is A. C. nf a hmm selected to `detect,:defects of a depth. 11ans, ortheetecma ofsunoefaiiguecrackxm cycleLisprrenble.' Theadnnbxennsing C iesn'thefactxatsuchcmmtstaysnear otmatewhennasusedsnthelatterpenemtes the entire cross- Hen, n defect will medtaazngcrpementlgeofthetotalmlnme thrmzghwhich/Aaspassngtlmnwouldbe theaif'D.fC.werensed. However-,ifdeep internal defectsnetnbedetected itmaybe neoessaxytoemplayllc.

manepossiblewnrebuthdfthenumberof pairs-ofeuntactsnean'angednshsw'edrehlihresetofcontents 1?",lil,Ms'ecnnnectmiinparfalelasisthexletof ycontacts '13, il, 15, and each otact may coopycratewzitirrrmeor'xnomenf'theeontmctsnthe 1" u .Eden du l In amordnnoe with the of the patinerxtstutxiters,wehmmelzneneintheprindple and'opemtmnfurr'invmtion, together withthe npmzatuswhichwemweonsdertomesmtthe besttheeothrtwedesiretnhavet illustrative'andtbattheinvention canbe carriedoutbyotl'equivalentmeans. Alsmwhile it is `designed to use the various features and elements in the combination and relation described, some of these may be altered and others omitted without interfering with the more general results outlined, and the invention extends to such use. v

Having described our invention, what we claim and desire to secure by Letters Patent is:

1. In a aw detector mechanism for electricalI conductors, means for passing current through said conductor along a predetermined current axis, and means for detecting variations in the current caused by defects in said conductor, said lastsnamed means comprising two sets of con- 1 tacts, one set spaced from the other set along the current axis, each contact of one set ,cooperating with the respective contact in the other set to form a pair of contacts formeasuring po tential drop along the current axis, the contacts oi one set being staggered with respect to the contacts o the other set.

2. In a aw detector mechanism for elongated conductors such as struts and the like, a source of current, means for supporting struts of different lengths under tension and effecting electrical contact between said struts and said support, said means comprising relatively movable supports of conductive material in electrical engagement with said current source, each support having an aperture large enough to support struts of various dimensions, end members of cony ductive material adapted to be mounted on the supports o1 conductive material in electrical engagement with said current source, each support having a U-shaped aperture large enough to support struts of various dimensions, end mem' bers of conductive material adapted to be mounted on the ends of the struts in electrical contact therewith and positioned outside of said supports so that movement of said supports away from each other causes the strut to be subjected to tension, and means whereby said supports are adapted to be moved relatively to effect Contact between said end members and said supports,

4. In a flaw detector mechanism for elongated conductors such as struts and the like, a source of current, means for supporting struts of different lengths under tension and effecting electrical contact between said struts and said sup port, said means comprising relatively movable supports of conductive material in electrical engagement with said current source, each support having a U-shaped aperture large enough to support struts of various dimensions, said 'struts having their ends threaded, end members of conductive material adapted to be threaded on the ends of the struts in electrical contact therewith and' positioned outsideof said supports so thatvmovement of said supports away from each other causes the strut to be subjected to tension, and means whereby said supports are adapted to be -movedrelatively to eiect contact between said end members and said supports.'

5. In a flaw detector mechanism for electrical conductors, means for passing current through said conductor along a predetermined axis, and means for detecting variations in the current caused by defects in said conductor, said last named means comprising a plurality of sets of contacts so positioned that lines joining each contact of one set with every contact of the other set will all be angularly displaced with respect to the current axis.

LOREN J. DE LANTY.

WILLIAM A. WILLIAMS. 

